Creating password protected folders

Hi,

I am newbie and have been assigned with a project where I need to create an option in zimbra webmail to make password protected folders. As well as these passwords can be different from the account login password. I have no idea how to do it. IT would be very appreciative if anbody can give me some idea about how to write a code for password protected folders and integrate it with current zimbra, and i need to do it all on Centos/Linux OS. Badly need help.